A data processing apparatus which displays a set of document data on a display unit together with an operation menu which has operation items related to the set of document data. In the apparatus, the document data storage unit stores a plurality of sets of document data of different contents which are indicated by sets of content information. The operation menu information storage unit stores a plurality of sets of operation menu information which each contain operation items that correspond to a content of document data. The first indication operation unit indicates a display of a set of document data. The second indication operation unit indicates an addition of a display of an operation menu to a display of document data. The operation menu generation unit receives an indication from the second indication operation unit, obtains the content information of the displayed data from the document data storage unit, extracts a corresponding set of operation menu information from the operation menu information storage unit, and generates an operation menu with the extracted operation items as menu items. The display control unit reads a set of document data from the document data storage unit, has the data displayed on the display unit in accordance with an indication from the first indication operation unit, and has the operation menu generated by the operation menu generation unit displayed in a window provided on the display unit.